Low-flow-rate electromagnetic induction liquid lead bismuth flowmeter

Abstract

The invention provides an electromagnetic induction flowmeter capable of measuring low-flow-velocity lead bismuth fluid. The electromagnetic induction flowmeter is not in direct contact with high-temperature lead-bismuth liquid with metal corrosivity, and a generated voltage signal is strong enough at a low flow rate and is excellent in linearity. The main parts of the device comprise a base and two corrosion-resistant and high-temperature-resistant permanent magnet type strong magnets, and a stable and uniform magnetic field is formed in the middle of the device. And a lead-bismuth fluid pipeline passes through the N pole and the S pole of the magnet. Metal wires are fixed on the pipeline vertical to the magnetic field to transmit voltage signals to the differential amplifier, and the amplification multiplying power is calibrated by experiments. And the flow of the lead-bismuth liquid at low flow velocity can be stably and precisely measured.

Description

Technical Field

[0001] The invention relates to the field of lead-based fast reactors in fourth-generation nuclear reactors, and in particular belongs to an electromagnetic induction flowmeter for measuring the flow of low-flow liquid lead-bismuth metal by electromagnetic induction. Background Art

[0002] Lead-bismuth alloy is one of the preferred materials for coolant of the fourth generation lead-based fast reactor. However, due to its corrosiveness to steel, the oxygen concentration in the alloy needs to be controlled. The oxygen concentration regulation performance is related to the flow rate of the lead-bismuth fluid in the system. And the oxygen concentration control technology needs to measure the flow rate at low flow rate. Due to the special physical and chemical properties of liquid lead-bismuth alloy and the high temperature environment, ordinary flow meters are limited. The pipeline components of the vortex street and targeted flowmeters in the commonly used liquid metal flowmeters are easily damaged by lead and bismuth; the differential pressure flowmeter is difficult to measure low-speed fluids, and the oxide impurities in lead and bismuth are easy to block the small-diameter venturi pipes; the temperature flowmeter is also not suitable for measuring low-flow fluids; the ultrasonic flowmeter uses the Doppler principle, with a large measurement range, but its probe has poor high-temperature resistance, and the low frequency is nonlinear due to the influence of impurities. For the system space with low flow and low pressure drop, the permanent magnet electromagnetic induction flowmeter (PMFs) has the advantages of simple structure, strong output signal, excellent linearity, high temperature resistance and insensitivity to fluid flow characteristics, and is an ideal device for measuring lead-bismuth flow. Summary of the invention

[0003] The technical problem solved by this invention is to measure the flow rate of lead-bismuth alloy at a low flow rate in liquid lead-bismuth oxygen control technology. In the high temperature and corrosive environment of the lead-bismuth fluid, the electromagnetic induction principle can be used to measure the electric induction signal generated by the lead-bismuth conductive metal fluid in a strong magnetic field, thereby achieving accurate measurement of the lead-bismuth flow rate.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows: a low-flow electromagnetic induction liquid lead-bismuth flowmeter, wherein a magnet fixing base (2) is fixed by an internal fixing screw (3) and an external screw (10) through a base (1), and a permanent magnet (4) is fixed on the base to generate a strong magnetic field. A lead-bismuth fluid pipeline (5) passes through the middle part and is fixed by an upper fixing ring (8) and a lower fixing seat (9). The conductive lead-bismuth fluid cuts the magnetic flux lines to generate a sufficiently strong electrical signal, and the voltage signal is transmitted to a primary differential amplifier through an upper metal wire (6) and a lower metal wire (7) to adjust the amplification factor.

[0005] Wherein, the base (1), the fixed magnet fixed base (2), the inner fixing screw (3), the outer screw (10), the lead-bismuth fluid pipeline (5), the upper fixing ring (8) and the lower fixing seat (9) are made of stainless steel.

[0006] The permanent magnet used is a corrosion-resistant and heat-resistant rectangular samarium cobalt (SmCo) permanent magnet, with the two magnetic poles close to the pipeline being the N pole and the S pole, to form a uniform strong magnetic field. There is no direct contact between the permanent magnet probe and the lead-bismuth probe to avoid extreme high temperature environments.

[0007] When lead and bismuth flow perpendicularly to the magnetic field at a certain speed as a conductive medium, an induced electromotive force is generated in the medium, and the flow meter signal is obtained through the potential difference between the electrodes of the upper metal wire (6) and the lower metal wire (7). The upper metal wire (6) and the lower metal wire (7) are made of high-temperature resistant and non-magnetized stainless steel. They are fixed by screwing.

[0008] The sizes of the upper fixing ring (8) and the lower fixing seat (9) are adjustable, and the thickness of the middle pipe is replaceable.

[0009] Among them, the anti-corrosion technology of lead-bismuth fluid pipelines requires controlling the oxygen concentration to form an insulating oxide layer on the inner surface of the pipeline to attenuate the voltage signal. Therefore, the amplification factor of the primary differential amplifier is calibrated by experiment.

[0010] The beneficial effects of the present invention are as follows: the present invention has a simple structure, does not contact with high-temperature metal-corrosive lead-bismuth liquid metal, has high reliability, is easy to load and unload and maintain, uses corrosion-resistant and heat-resistant rectangular samarium cobalt (SmCo) permanent magnets to generate a uniform strong magnetic field, and low-flow liquid metal can also generate a sufficiently strong voltage signal. Lead-bismuth anti-corrosion technology requires controlling the oxygen concentration to form an insulating oxide layer on the inner surface of the pipeline to attenuate the voltage signal. Since the voltage signal generated by the permanent magnet flowmeter has good linearity, it only needs to calibrate the differential amplifier gain through a calibration test. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of voltage signal generated by liquid metal fluid cutting strong magnetic field lines of flux;

[0012] Figure 2 This is the structural diagram of a low-flow-rate permanent-magnet liquid lead-bismuth flowmeter;

[0013] Figure 2 In the embodiment, there are a base (1), a magnet fixing base (2), an internal fixing screw (3), a permanent magnet (4), a lead-bismuth fluid pipeline (5), an upper metal wire (6), a lower metal wire (7), an upper fixing ring (8), a lower fixing seat (9), and an external screw (10). DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0015] The present invention provides a low-flow electromagnetic induction liquid lead-bismuth flowmeter, in which the magnet and the lead-bismuth electrode wire are not in direct contact, thus avoiding the high-temperature and corrosive lead-bismuth fluid environment. Through the electromagnetic induction principle, the electric induction signal generated by the lead-bismuth conductive metal fluid can be measured in a strong magnetic field, thereby realizing accurate measurement of the flow rate of the lead-bismuth low-flow fluid.

[0016] like Figure 1 As shown, the liquid metal fluid cuts the magnetic flux lines of the strong magnetic field to generate a voltage signal principle diagram. The corrosion-resistant and heat-resistant rectangular samarium cobalt (SmCo) permanent magnets on both sides generate a uniform strong magnetic field inside the pipeline, and the flowing conductive medium lead bismuth cuts the magnetic flux lines in the middle pipeline to generate a voltage signal.

[0017] According to the electromagnetic flow rate theoretical calculation formula, the calculation formula for the voltage at the electrode wire end after the liquid metal fluid cuts the magnetic field is:

[0018] Where U th is the theoretical output voltage of the flow meter, in V; T room and T represent the experimental temperature and the ambient temperature, respectively, in °C; B represents the magnetic flux of the permanent magnet, in T; α and β represent the expansion coefficient of the pipeline material and the temperature coefficient of the magnet, respectively; d in Indicates the inner diameter of the pipe, in m; Q th is the theoretical volume flow rate, unit: m 3 ·s, and U th correspond.

[0019] f 1 , f 2 are the correction coefficients for the wall shunt effect and the end shunt effect, respectively, 1 The calculation formula is:

[0020] Where, d in and d out Respectively represent the inner and outer diameters of the flow channel, unit: m; δ w , δ f Represent the electrical conductivity of the pipeline material and the fluid medium respectively.

[0021] End shunt effect correction factor f 2The size depends on the ratio of the axial length of the magnet along the flow channel to the inner diameter of the flow channel.

[0022] like Figure 2 As shown, a permanent magnet lead-bismuth liquid metal flowmeter is provided. A magnet fixing base (2) is fixed by a base (1) using an internal fixing screw (3) and an external screw (10). A rectangular samarium cobalt (SmCo) permanent magnet (4) is fixed on the base to generate a strong magnetic field. A 316L stainless steel lead-bismuth fluid pipeline (5) with an inner diameter of 8 mm and an outer diameter of 12 mm is passed through the middle part and is fixed by an upper fixing ring (8) and a lower fixing seat (9). The conductive lead-bismuth fluid cuts the magnetic flux lines to generate a sufficiently strong electrical signal, and the voltage signal is transmitted to a primary differential amplifier through a 316L upper metal wire (6) and a lower metal wire (7) with a diameter of 1 mm to adjust the amplification factor.

[0023] Due to the need for low flow rate measurement and the signal attenuation caused by corrosion on the inner surface of the electromagnetic flowmeter measuring pipe after long-term operation, the electrical signal needs to be amplified by a differential amplifier. When the linear coefficient of the voltage and fluid flow of the calibration result differs by more than 30% from the original, the intermediate measuring pipe should be replaced.

[0024] According to the calibration experiment results, the low-flow-rate and high-temperature liquid metal flow rate is measured in the temperature range of 300℃ to 375℃. The actual readings of the calibrated volume flow and voltage meet the following requirements: Q cal =0.56548×U real 3

[0025] In the formula, Q cal is the volume flow rate after calibration, in m 3 h -1 ; U real It is the actual measured voltage signal, in mV.

[0026] In summary, the low-flow rate permanent magnetic liquid lead-bismuth flowmeter of the present invention can measure high-temperature corrosive liquid lead-bismuth fluid, has a simple structure and is not easy to damage. It has few parts and is easy to update and maintain. It has good linearity and can measure low-flow rate flow using a strong magnetic field. It can be calibrated repeatedly to ensure the accuracy of the results.

Claims

1. A low-flow electromagnetic induction liquid lead-bismuth flowmeter, wherein a base (2) is fixed to a magnet by means of an inner fixing screw (3) and an outer screw (10) through a base (1), and a permanent magnet (4) is fixed on the base to generate a strong magnetic field. A lead-bismuth fluid pipeline (5) passes through the middle and is fixed by means of an upper fixing ring (8) and a lower fixing seat (9). The conductive lead-bismuth fluid cuts the magnetic flux lines to generate a sufficiently strong electrical signal, and the voltage signal is transmitted to a primary differential amplifier through an upper metal wire (6) and a lower metal wire (7) to adjust the amplification factor.

2. A low flow rate electromagnetic induction liquid lead bismuth flowmeter according to claim 1, characterized in that: The permanent magnet (4) uses a corrosion-resistant and heat-resistant rectangular samarium cobalt (SmCo) permanent magnet to generate a uniform strong magnetic field. Avoid high temperature extreme environment, and no permanent magnet probe directly contacts the lead bismuth.

3. A low flow rate electromagnetic induction liquid lead bismuth flowmeter according to claim 1, characterized in that: The lead-bismuth fluid flows through the lead-bismuth fluid pipeline (5), the upper part of which is fixed by a fixing ring (8) and the lower part is fixed by a fixing seat (9). The middle pipeline can be replaced.

4. A low flow rate permanent magnet liquid lead bismuth flowmeter according to claim 1, characterized in that: The voltage signal is attenuated due to lead-bismuth corrosion and the formation of an insulating oxide layer. The flow meter can be calibrated repeatedly. Specifically, the differential amplifier ratio is determined experimentally.

5. A low-flow rate permanent magnetic liquid lead-bismuth flowmeter according to claim 1, characterized in that: The calculation formula for the voltage at the electrode wire end after the liquid metal fluid cuts the magnetic field is: Among them, f1 and f2 are the correction coefficients of wall shunt effect and end shunt effect, respectively. The calculation formula of f1 is: The end shunt effect correction coefficient f2 depends on the ratio of the axial length of the magnet along the flow channel to the inner diameter of the flow channel. According to the calibration test results, the low-flow-rate and high-temperature liquid metal flow rate is measured in the temperature range of 300℃ to 375℃. The actual readings of the calibrated volume flow and voltage meet the following requirements: Q cal =0.56548×U real 3 In the formula, Q cal is the volume flow rate after calibration, in m 3 h -1 ; U real It is the actual measured voltage signal, in mV.

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